To map the universe, astronomers string together distance measurements to ever-farther objects, like climbing rungs on a cosmic ladder.   The cosmic distance ladder allows astronomers to confidently measure vast distances.   When humans look up at the night sky, they naturally ask the question: How far away is that planet, or that star, or that galaxy? Distance is one of the most fundamental measurements astronomers make, but it’s also one of the most challenging. Fortunately, astronomers have a vital tool to help them answer that central question: how far? That tool is the cosmic distance ladder. This ladder has “rungs” of objects with certain properties that let astronomers confidently measure their distance. Jumping to each subsequent rung relies on methods for measuring objects that are ever farther away, the next step often piggybacking on the previous one. For example, once astronomers measure the distance to a galaxy using one r...

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What are black holes?

Friday, July 12th 2019 01:29 PM

Black holes are some of the strangest and most fascinating objects in outer space. They're extremely dense, with such strong gravitational attraction that even light cannot escape their grasp if it comes near enough.  Albert Einstein first predicted the existence of black holes in 1916, with his general theory of relativity. The term "black hole" was coined many years later in 1967 by American astonomer John Wheeler. After decades of black holes being known only as theoretical objects, the first physical black hole ever discovered was spotted in 1971.  Then, in 2019 the Event Horizon Telescope (EHT) collaboration released the first image ever recorded of a black hole. The EHT saw the black hole in the center of galaxy M87 while the telescope was examining the event horizon, or the area past which nothing can escape from a black hole. The image maps the sudden loss of photons (particles of light). It also opens up a whole new area of research in black holes, now that astro...

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Around the Milky Way are more than 150 globular clusters, ancient star cities with hundreds of thousands of closely packed denizens. Most such clusters can be found out in the galaxy’s nearly empty halo; it’s likely they formed before our galaxy did. But one of these is not like the others. A view of the iconic Omega Centauri globular cluster.ESO / INAF-VST / OmegaCAM; Acknowledgement: A. Grado, L. Limatola / INAF-Capodimonte Observatory Omega Centauri (NGC 5139, or Omega Cen for short) is unusually brilliant, massive, and huge: 10 million stars squeeze into a sphere about 150 light-years wide. What most puzzles astronomers, though, is that its stars come in at least three distinct populations, suggesting the cluster came together over billions of years instead of all at once. Astronomers have long thought this peculiar globular might be something else altogether: the remains of a galaxy that came too close to the Milky Way. Torn apart by our galaxy’s...

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Astronomers Find Second Galaxy with No Dark Matter

Monday, April 22nd 2019 01:32 PM

“Discovering a second galaxy with very little to no dark matter is just as exciting as the initial discovery of DF2,” Yale University’s Professor Pieter van Dokkum. “This means the chances of finding more of these galaxies are now higher than we previously thought. Since we have no good ideas for how these galaxies were formed, I hope these discoveries will encourage more scientists to work on this puzzle.” The newly-discovered galaxy, named NGC 1052-DF4 (DF4 for short), resembles DF2 in terms of its size, brightness, and morphology, and has a similar distance of 65 million light-years. “Like DF2, it belongs to a recently-discovered class of galaxies called ultra-diffuse galaxies (UDGs),” the astronomers said. “They are as large as the Milky Way but have between 100 to 1,000 times fewer stars, making them appear fluffy and translucent, therefore difficult to observe.” “Ironically, the lack of dark matter in thes...

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A new neutron star merger is caught on X-ray camera

Friday, April 19th 2019 02:22 PM

In October 2017, astronomers announced the first detection of gravitational waves from the merger of two neutron stars earlier that year. The event also rung in the era of multi-messenger astronomy, as more than 70 telescopes observed the event’s afterglow in optical light, X-rays, gamma rays, and more. Now, an X-ray signal dubbed XT2 from a galaxy 6.6 billion light-years away has revealed another neutron star merger, which left behind a single, heavier neutron star with an incredibly powerful magnetic field: a magnetar. “We’ve found a completely new way to spot a neutron star merger,” said Yongquan Xue of the University of Science and Technology of China in a press release. Xue is lead author of a paper on the finding, published April 11 in Nature. Furthermore, he says, “The behavior of this X-ray source matches what one of our team members predicted for these events.” Signals of a merger When neutron stars spiral together and mer...

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Around 40% of new astronomy faculty in US universities are women, while a quarter of new physics faculty recruits are female. That is according to data from a recent report by the American Institute of Physics (AIP), which also finds an increase in female representation at postgraduate levels as well as a boost in the proportion of Hispanic women taking physics. The report — Women in Physics and Astronomy, 2019 — is based on several different surveys that were conducted at physics and astronomy departments across the US. The report finds that, at postgraduate level, the percentage of physics and astronomy doctorates earned by women has risen in the past decade, with 20% of physics and 40% of astronomy doctoral degrees awarded to women in 2017 — up from 18% and 28% in 2007, respectively. We probably need to do more than just wait for the increase to happen to make many of the department cultures fully welcoming to women Th...

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Astronomers Find Universe’s First Molecule

Wednesday, April 17th 2019 12:02 PM

A team of astronomers and a high-flying observatory have finally found the helium hydride ion— the first molecule to come together in the cosmos — in interstellar space. “The unambiguous detection reported here brings a decades-long search to a happy ending at last,” write Rolf Güsten (Max-Planck Institue for Radio Astronomy, Germany) and colleagues in the April 18th Nature. Back when the universe was in its infancy, its soup of matter and radiation was too hot to allow the formation of anything like the atoms and molecules that make up the world around us today. Only once the universe turned some 380,000 years old had it cooled enough for protons and neutrons to combine into atoms. (Even then, it remained pretty hot at 4000K, not quite as scalding as the Sun’s visible surface.) Then atoms combined into molecules. In the Beginning Given that the universe was largely hydrogen and helium at this time, it’s perhaps no surprise that the uni...

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The Sky This Week from April 12 to 21

Friday, April 12th 2019 12:00 PM

Friday, April 12First Quarter Moon arrives at 3:06 p.m. EDT. You can find the half-lit orb high in the southwest as darkness falls; it doesn’t set until nearly 3 a.m. local daylight time tomorrow morning. The Moon currently lies on the border between Gemini and Cancer, about 10° south of the Twins’ brightest stars, Castor and Pollux.Saturday, April 13Mercury lies low in the eastern sky before dawn all week. This morning, it appears some 4° high 30 minutes before sunrise. The innermost planet glows at magnitude 0.2 and should appear as an inconspicuous dot to the naked eye, but it stands out through binoculars. Use Venus, which shines brilliantly some 4° to Mercury’s upper right, as a guide.     Pallas near its best The second asteroid to be discovered remains near peak visibility this week as it slides northwest relative to the background stars of Boötes the Herdsman. Astronomy: Roen Kelly Sunday, April 14Asteroid...

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Now the methane's gone: A martian mystery deepens

Thursday, April 11th 2019 11:58 AM

The European Space Agency’s ExoMars spacecraft failed to find any traces of methane on the Red Planet during its hunt from April to August of 2018. This goes directly against recent positive reports of methane by ESA’s own Mars Express spacecraft and NASA’s Curiosity rover, which both saw methane in 2013. ExoMars has a sensitive detector that can pick up just one-tenth the amount of methane that Mars Express witnessed. That leaves two options: either one set of observations is in error, or something happened to the methane in the intervening time. The latter option is gaining traction. Given the years-long history of conflicting methane reports on Mars, it’s looking more and more likely that the methane is real. But some unknown process or force *must be* causing it to disappear inexplicably fast. Piling up the data The new findings, like the old ones, make some scientists wary, especially given thepossible implications of methan...

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Where Did Earth's Water Come From?

Wednesday, April 10th 2019 01:47 PM

Karen Meech doesn’t spend a lot of time digging through Earth’s rocks. An astronomer by trade, she is usually behind the telescope, investigating comets and looking for hints about how Earth got its water. But a field trip to Iceland in 2004 ultimately sent her scrambling through the craters of Hawaii nearly a decade later in search of clues about the liquid that helped birth life on this planet.  On that fateful Icelandic tour, Meech saw geothermal areas with gas billowing out of the ground. The guide told the group not to worry — it was only water. “Then she said, ‘This is probably primordial water,’ and it set a lightbulb off,” Meech says. The flavors of water The source of Earth’s water has been a long-standing mystery; Meech herself has been trying to solve it for at least 20 years. Most of that search has focused on sorting out the various isotopes of hydrogen that go into making the water — or “the flavor...

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